A Donor Pledged $500,000 to a Not-For-Profit Hospital in 2016

A donor pledged $500,000 to a not-for-profit hospital in 2016 to conduct medical research, conditional on the hospital raising $500,000 from other donors. The other donors met the condition in 2016 The donor transferred the funds to the hospital in 2017. In which year would the revenue be recognized?

A) 2016.
B) 2017.
C) Half in 2016 and half in 2017.
D) None of the above; the hospital would only recognize revenue when the amounts had been expended according to the donor's wishes.